不知凡幾

one can't tell how many / numerous similar cases

no; not so / (bound form) not; un-

not to know / unaware / unknowingly / fig. not to admit (defeat, hardships, tiredness etc)

to know / to be aware

ordinary / commonplace / mundane / temporal / of the material world (as opposed to supernatural or immortal levels) / every / all / whatever / altogether / gist / outline / note of Chinese musical scale

variant of 凡[fan2]

almost

how much / how many / several / a few